Mold structures, and method of transfer of fine structures
A mold and a pattern transfer method using the same for a nanoprinting technology. The mold can be released from a substrate accurately and easily. The mold, which is used for forming a fine pattern on a substrate using a press machine, comprises a release mechanism.
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This application is a divisional application of U.S. application Ser. No. 10/802,816, filed Mar. 18, 2004, now abandoned the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Technical Field
The present invention relates to a nanoprint transfer method for forming a fine structure on a substrate using a mold comprising a heating and a pressure-applying mechanism.
2. Background Art
In recent years, the semiconductor integrated circuits are becoming increasingly finer and more integrated. To cope with such size reductions and increased levels of integration, the accuracy of the photolithography equipment as a pattern transfer technology has been continuously improved. However, the processing method now involves a scale close to that of the wavelength of the photolithographic light source, and the lithography technology is close to its limit. As a result, in order to allow for further reductions in size and achieve higher accuracy, electron beam lithography equipment, which is a type of charged-particle beam equipment, has come to be used more often than photolithography technology.
When patterns are formed using an electron beam, in contrast to the one-shot exposure method whereby an i-line or excimer laser light source is used for forming patterns, a mask pattern is drawn. Accordingly, the electron beam pattern forming method takes more time for exposure (drawing) as the number of patterns to be drawn increases, disadvantageously resulting in increased time for pattern formation. Thus, as the level of integration greatly increases from 256 MB to 1 GB to 4 GB, the time required for pattern formation also increases greatly, possibly resulting in significantly lowered throughput. Thus, in order to reduce time required by the electron beam lithography equipment, development of a one-shot pattern irradiation method is underway whereby masks of various shapes are combined and are irradiated with an electron beam in a single shot, and electron beams of complex shapes are formed. While this allows ever finer patterns to be obtained, it also results in an increase in the size of the electron beam lithography equipment, and it requires a mechanism for controlling mask positions more accurately, thereby increasing equipment cost.
Technologies for carrying out fine pattern formation at low cost are disclosed in U.S. Pat. No. 5,259,926, U.S. Pat. No. 5,772,905 and S. Y. Chou et al., Appl. Phys. Lett., vol. 67, p. 3314 (1995), for example. According to these technologies, a mold having the same concave-convex pattern of as that which is desired to be formed on a substrate is stamped on a resist film layer formed on the surface of the substrate, thereby transferring a predetermined pattern onto the substrate. Particularly, it is described in U.S. Pat. No. 5,772,905 and S. Y. Chou et al., Appl. Phys. Lett., vol. 67, p. 3314 (1995) that the disclosed nanoimprint technique, using a silicon wafer as a mold, can transfer and form fine structures of not more than 25 nanometers.
SUMMARY OF THE INVENTIONHowever, even with the imprint technique that is supposed to be capable of forming a fine pattern, it is difficult to release a mold from the substrate once the mold has been pressed thereon, with high accuracy and without deforming the fine concave-convex pattern formed on the substrate. For example, when a silicon wafer is used as a mold, the mold could be damaged upon its release.
SPIE'S Microlithography, Santa Clara, Calif., Feb. 27-28, 2001 discloses that a release treatment is provided for the mold that is then mechanically released. In this method, however, the problem of damage to the mold upon release has not yet been solved.
In view of the foregoing, it is the object of the present invention to provide a nanoprint method that is a pattern transfer technique for forming fine structures during the manufacture of semiconductor devices, for example, whereby the mold can be easily and accurately released from the substrate.
The present invention is based on the understanding that one of the reasons preventing the efficient release of the mold is that the arrangement of the substrate and mold is too rigid.
In one aspect, the invention provides a mold for forming a fine structure on a substrate using a press machine. The mold, which is for nanoprinting, is provided with a release mechanism, which facilitates the release of the mold from the substrate.
The invention also provides a nanoprint mold for forming a fine structure on a substrate using a press machine, wherein a portion of a periphery portion of said mold on the side where the concave-convex pattern is formed is inclined such that a center portion of the substrate has a large thickness. By increasing the thickness at the center portion of the mold, the substrate, which is warped during the press process, tries to regain its original state during the release step, creating a stress that facilitates the release of the mold from the substrate. Thus, the mold can be easily released from the substrate at a point where the stress is created.
The invention also provides a nanoprint mold for forming a fine structure on a substrate using a press machine, wherein the mold is flexible. Because the mold is flexible, damage to the mold and/or the substrate that can occur if a local stress is applied between the substrate and the mold during the release step can be prevented.
Preferably, the mold is secured to a supporter via an elastomer. By thus securing the mold to the supporter via an elastomer, the force existing between the substrate and the mold can be made more flexible so that damage to the substrate and/or the mold can be effectively prevented.
Preferably, the supporter comprises a rectangular, square, circular, or elliptical frame structure. By adopting such a frame structure, the mold can be secured to the supporter via the elastomer in a minimal manner, and further a better operability can be obtained during the pattern transfer by a nanoprinting method.
The invention also provides a nanoprint mold for forming a fine structure on a substrate using a press machine, wherein said mold is provided with an elastomer at an edge of the side of said mold on which the concave-convex pattern is formed, said elastomer facilitating the release of said mold from said substrate.
The press machine may comprise a heating and pressing mechanism.
In another aspect, the invention provides a pattern transfer method for forming a fine structure on a substrate using a press machine and a nanoprint mold. A release mechanism is provided in the mold.
For example, the invention provides a pattern transfer method for forming a fine structure on a substrate using a press machine and a nanoprint mold, wherein a portion of a periphery portion of said mold on the side where the concave-convex pattern is formed is inclined such that a center portion of the substrate has a large thickness.
The invention also provides a pattern transfer method for forming a fine structure on a substrate using a press machine and a nanoprint mold having a heating and pressing mechanism, wherein the mold is flexible.
Preferably, the mold is secured to a supporter via an elastomer.
Preferably, the supporter comprises a rectangular, square, circular or elliptical frame structure.
A resin substrate or a resin film on a substrate is preferably molded by either: 1) heating and deforming the resin substrate or the resin film on the substrate; 2) pressing and molding the resin substrate or the resin film on the substrate and then optically curing the resin substrate or the resin film; or 3) optically curing the resin substrate or the resin film on the substrate.
Referring to
The nanoprint method offers various merits. For example: 1) it can transfer extremely fine integrated patterns with high efficiency; 2) it can reduce equipment cost; and 3) it can be used for complex shapes and is capable of forming pillars.
Fields of application of the nanoprint method are many, including: 1) various bio-devices such as DNA chips and immunoassay chips, particularly disposable DNA chips; 2) semiconductor multilayer wiring; 3) printed circuit boards and RF MEMS; 4) optical or magnetic storage; 5) optical devices, such as waveguides, diffraction gratings, microlenses and polarizers, and photonic crystals; 6) sheets; 7) LCD displays; and 8) FED displays. The present invention can be suitably applied to any of these fields.
The term “nanoprint” herein refers to the transfer of patterns or the like measuring several 100 μm to several nm.
While the press machine used in the present invention is not particularly limited, it is preferable to employ a machine equipped with a heating and pressing mechanism and/or a mechanism for shining light from above the light-transmitting mold, from the viewpoint of efficient pattern transfer.
In the invention, the method of forming the fine pattern on the mold that is to be transferred is not particularly limited. For example, photolithography, electron beam lithography, or other techniques may be employed, depending on the desired processing accuracy. The material for the mold may be any material as long as it has a desired strength and a required level of workability, such as silicon wafer, various metal materials, glass, ceramics and plastics. More specifically, examples include Si, SiC, SiN, polycrystalline Si, glass, Ni, Cr, Cu and combinations thereof.
The material for the substrate used in the present invention is not particularly limited, the only requirement being that it has a required strength. Examples include silicon, various metal materials, glass, ceramics and plastics.
The resin film onto which the fine structure is transferred in the invention is not particularly limited and may be selected from a variety of examples depending on the desired processing accuracy. The examples include thermoplastic resins such as: polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, polyvinyl chloride, polystyrene, ABS resin, AS resin, acrylic resin, polyamide, polyacetal, polybutylene terephthalate, glass-reinforced polyethylene terephthalate, polycarbonate, denatured polyphenylene ether, polyphenylene sulfide, polyetheretherketone, liquid crystal polymer, fluororesin, polyarylate, polysulfone, polyethersulfone, polyamide-imide, polyetherimide and thermoplastic polyimide; and thermosetting resins such as phenol resin, melamine resin, urea resin, epoxy resin, unsaturated polyester resin, alkyd resin, silicone resin, diallyl phthalate resin, polyaminobismaleimide and poly-bis-amide-triazole; and materials in which two or more of the above-mentioned materials are blended.
EXAMPLESExamples of the invention will be hereafter described.
Example 1Referring to
Now referring to
Referring to
The Ni mold (6 inches, 100 μm in thickness) produced by the above-described process was bonded to an SUS (6 inches, with a thickness of 1 cm at the center and 7 mm at the edges) using a silicone adhesive (KE1820, manufactured by Shin-Etsu Silicones), and a pressure was exerted thereon (
Alternatively, it is possible to make a curved mold by performing Au 20-nm sputtering on a concave mold, conducting Ni electroplating until the center portion has a thickness of approximately 1 cm, and then releasing the deposited mold from the concave mold. Further, it is also possible to produce a concave mold by providing Ni plating on a convex mold in a similar manner.
Hereafter, the stamping process using a convex mold will be described by referring to
A method of producing a mold with a curved surface in which a deep groove is formed according to another embodiment of the invention will be described by referring to
A cross-shaped pattern with a width of 10 μm and a depth of 3 μm was formed in advance at the center of a Ni mold (6 inches, 100 μm in thickness). The mold was then bonded to an SUS (6 inches, with a thickness of 1 cm at the center and 7 mm at the edges), with a silicone adhesive (KE1820, manufactured by Shin-Etsu Silicones), thereby obtaining a deep-grooved convex mold (
A stamping process was carried out using the above-described convex-curved mold with the deep groove. A 10% diethylene glycol monoethyl ether acetate solution of polystyrene 679 (manufactured by A & M Styrene Co., Ltd.) was applied to a 5-inch Φ Si substrate with a thickness of 0.5 mm, to a thickness of 500 nm. A 4-inch Φ buffer material of a thickness of 3 mm was then placed underneath. The base of the press machine had been formed to have a concave-curved surface in advance (
Similar effects were obtained with a concave-curved mold with a deep groove as shown in
A method of producing a mold with elastic edges according to another embodiment of the invention will be described by referring to
A stepped Ni mold (4-inch Φ, with a 1-cm band portion at the periphery measuring 1 mm in thickness, a pattern-formed portion measuring 5 mm in thickness, and a pattern measuring 300 nm in depth) was affixed to an SUS frame (6-inch Φ; 1 mm in thickness), using a silicone adhesive (KE1820, Shin-Etsu Silicones). A silicone rubber member (6 mm square in cross section) was affixed to the periphery of the mold using the aforementioned adhesive.
A 10% diethylene glycol monoethyl ether acetate solution of polystyrene 679 (manufactured by A & M Styrenes) was applied to a 5-inch Φ Si substrate with a 0.5 mm thickness to a thickness of 500 nm (
Similar effects were obtained when an elastomer was affixed to a Ni mold provided with a tapered edge, as shown in
Referring to
A silicone rubber member as an elastomer with a hollow center and with a thickness of 1 mm was affixed to a quartz mold (VIOSIL: manufactured by Shin-Etsu Chemical Co., Ltd., 5-inch Φ and 6.35 mm in thickness) using a silicone adhesive (KE1820, manufactured by Shin-Etsu Silicones). An SUS frame was further affixed as a supporter. A photosetting resin (SCR701, manufactured by JSR) was spin-coated on a quartz substrate (VIOSIL: Shin-Etsu Chemical Co., Ltd., 5-inch Φ and 6.35 mm in thickness), to a thickness of 500 nm (
Examples of the Application of the Invention
Hereafter, several fields to which the nanoprinting technique using the mold with a release-mechanism according to the invention can be suitably applied will be described.
Example 6 Bio (Immuno) ChipWhile in the present embodiment there is only one flow passage 902, a plurality of flow passages 902 in which projections of different sizes are disposed may be provided. In this way, different kinds of analysis can be performed simultaneously.
While in the present embodiment DNA was examined as specimen, a particular sugar chain, protein or antigen may be analyzed by modifying the surface of the projection assembly 100 in advance with a molecule that reacts with the sugar chain, protein or antigen. By thus modifying the surface of the projections with an antibody, improvements can be made in the sensitivity of immunoassay.
By applying the invention to a biochip, a projection for the analysis of organic materials with nanoscale diameters can be simply formed. Further, by controlling the shapes of the concave and convex portions on the mold surface or the viscosity of the organic material thin film, the position, diameter and/or height of the projection made of organic material can be controlled. Thus, in accordance with the invention, there can be provided a microchip for high-sensitivity analysis.
Example 7 Multilayered Wiring BoardAnother process for making a multilayer wiring board will be hereafter described. Upon dry-etching of the exposed regions 703 in the state shown in
By applying the invention to a multilayer wiring board, wires can be formed with high dimensional accuracy.
Example 8 Magnetic DiscFor the mold, a Si wafer was prepared in which grooves were formed concentrically with the opening at the center of the magnetic recording medium. The grooves measured 88 nm in width and 200 nm in depth, and the pitch between the grooves was 110 nm. The convex and concave portions of the mold, which were very fine, were formed by photolithography using an electron beam. After heating the mold to 250° C. to reduce the viscosity of the resin, as shown in
Another example will be described in which an optical device with varying directions of propagation of incident light is applied to an optical information processing apparatus.
In the optical circuit 500, the directions of propagation of light can be varied when ten different wavelengths of signal light are superposed and outputted, so that the width of the circuit can be greatly reduced, to 5 mm in the example. Thus, the size of the optical communication device can be reduced. The projections 406 can be formed by the pressing of a mold, and manufacturing cost can be reduced. While the present example relates to a device in which input light is superposed, it should be obvious that the optical waveguide 503 can be usefully applied to all optical devices for controlling an optical path.
By applying the present invention to optical waveguides, the direction of propagation of light can be varied by causing a signal light to propagate in a structure where projections made of an organic material as a principal component are periodically arranged. The projections can be formed by a simple manufacturing technique involving the pressing of a mold, such that an optical device can be manufactured at low cost.
In accordance with the invention, a release mechanism is provided in a nanoprint mold by, in particular, increasing the thickness of a center portion of the mold. By so doing, the substrate is warped during the pressing step and then tries to regain its original state as the mold is released in the release step, creating a stress causing the substrate and mold to separate from each other. Thus, the release of the mold from the substrate is facilitated at a point where the stress exists. Further, in accordance with the invention, a flexible mold is employed such that the damage to the substrate and/or the mold that could result if a local stress is applied between them during the releasing of the mold can be prevented. In accordance with the invention, additionally, a spring mechanism is provided between the mold and the substrate whereby the release of the mold from the substrate is facilitated during the release step.
Claims
1. A pattern transfer method comprising the steps of:
- positioning a substrate, while in an original flat state and having a resin film formed thereon, onto a flat, solid buffer material positioned on a curved press machine base;
- pressing a stamper having a curved surface at a side on which a concave-convex pattern is formed onto the resin film to transfer said concave-convex pattern onto the resin film while smoothly warping the positioned substrate from said original flat state along the curved surface of the stamper and into conformity with the curvature of the base;
- removing the buffer material from the warped substrate; and
- lifting the stamper from the warped substrate and patterned resin after removing the buffer material and after release-start points are initially formed as a result of a force exerted by the substrate as the substrate returns from the warped state to said original flat state.
2. The pattern transfer method according to claim 1, wherein the stamper comprises a deep groove that is deeper than the concave-convex pattern, and wherein the deep groove penetrates the stamper from one side surface thereof to another side surface thereof.
3. The pattern transfer method according to claim 1, wherein the curved surface of the stamper is convex, and wherein the curve of the curved base is concave.
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Type: Grant
Filed: Jun 19, 2012
Date of Patent: Jan 21, 2014
Patent Publication Number: 20120256346
Assignee: Hitachi, Ltd. (Tokyo)
Inventors: Masahiko Ogino (Hitachi), Akihiro Miyauchi (Hitachi), Sigehisa Motowaki (Hitachi), Kosuke Kuwabara (Hitachi)
Primary Examiner: Atul P. Khare
Application Number: 13/526,708
International Classification: B28B 11/08 (20060101); B27N 3/18 (20060101); A01J 21/00 (20060101);